10.2: Animal Classification

Animal. What type? Now that is a good question. This azure vase sponge is an animal, but how is it classified? It is estimated that there are easily over a million species of animals on Earth. How are all these species divided into their various classifications?

Classification of Animals

All animals share basic traits. But animals also show a lot of diversity. They range from simple sponges to complex humans.

Major Animal Phyla

Members of the animal kingdom are divided into more than 30 phyla.
Table
below
lists the nine phyla with the greatest number of species. Each of the animal phyla listed in the table has at least 10,000 species.

Invertebrate vs. Vertebrate

The first eight phyla listed in
Table
above
include only invertebrate animals.
Invertebrates
are animals that lack a
vertebral column
, or
backbone
. The last phylum in the table, the Chordata, also includes many invertebrate species. Tunicates and lancelets are both invertebrates. Altogether, invertebrates make up at least 95 percent of all animal species. The remaining animals are vertebrates.
Vertebrates
are animals that have a backbone. All vertebrates belong to the phylum
Chordata
. They include fish, amphibians, reptiles, birds, and mammals.